Helminth Egg Removal Capacity of UASB Reactors under Subtropical Conditions

Abstract

This research was conducted to study the anaerobic sludge filtration capacity regarding helminth egg removal in upflow anaerobic sludge blanket (UASB) reactors. Two 25 L lab-scale UASB reactors were operated at an ambient temperature which varied between 17.1 and 28.6 °C. Ascaris suum egg was selected as the model egg considering its similarity in terms of size and morphology to Ascaris lumbricoides, a human pathogen. Ascaris suum eggs were obtained from female parasites of infected pigs. The anaerobic sludge filtration capacity was performed applying upflow velocities between 0.09 and 0.68 m·h −1. Three sludge bed heights in the range of 0.30-0.40 m, 0.50-0.60 m and 0.60-0.70 m were applied. These sludge bed heights corresponded to 19%-25%, 31%-38% and 38%-44% of the total reactor height, respectively. Under the mentioned conditions, the average helminth egg removal efficiency was reciprocally correlated to the imposed upflow velocity. The studied lab-scale reactors reported an average helminth egg removal between 34%-100%, 30%-91% and 34%-56%, when the sludge bed in the UASB reactor OPEN ACCESSWater 2015, 7 2403 was 19%-25%, 31%-38% and 38%-44% of the total reactor height, respectively. The decreased filtration capacity at increasing sludge bed heights might be likely related to biogas production and channeling formation. The average helminth egg removal efficiency in the control experiments performed without any sludge bed, by plain sedimentation, varied between 44% and 66%.

Increased (Antibiotic-Resistant) Pathogen Indicator Organism Removal during (Hyper-)Thermophilic Anaerobic Digestion of Concentrated Black Water for Safe Nutrient Recovery

“…In our study only UASB reactors, in which the HRT is uncoupled from the sludge retention time (SRT) [61], were assessed. Removal of pathogens can also be associated with filtration and sedimentation [62], so the SRT could be an additional factor in the pathogen removal. The effect of HRT and SRT on pathogen removal should be investigated in more detail.…”

Anaerobic Sludge Blanket Reactors

“…Table 5 presents concentrations of pathogens in the sludge. (Chernicharo et al 2001;Dixo et al 1995;Prado et al 2011;Soares et al 2000;von Sperling et al 2002von Sperling et al , 2003Keller et al 2004;Ribeiro et al 2015;El-Khateeb et al 2009;Morsy et al 2007;Trein et al 2015;Gonçalves et al 2009;Dias 2016;Verbyla 2015;Symonds et al 2014;Pant and Mittal 2007;Foxon 2009;Foxon et al 2006;Lalbahadur et al, 2005;Oliveira and von Sperling, 2011;von Sperling and Mascarenhas, 2005;Yaya-Beas et al, 2015) b ND = No data…”

“…1.0 log 10 removal for Salmonella spp., 0.5 log 10 removal for Shigella spp., 1.0 log 10 removal for Vibrio spp in a UASB reactor (Pant and Mittal, 2007) 1.1 log 10 reduction of thermotolerant coliforms in UASB reactors (Oliveira and von Sperling, 2011) 1.0 log 10 reduction of thermotolerant coliforms in an ABR reactor (Lalbahadur et al, 2005) 0.3 log 10 removal of Cryptosporidium oocysts (Morsy et al 2007) 0.42 to 1.30 log 10 for UASBs (Keller et al, 2004;von Sperling et al, 2003;Yaya-Beas et al, 2015).…”

Taenia spp.

“…The UASB reactor removes helminth eggs through a combination of sedimentation and egg entrapment within the sludge bed. A laboratory scale UASB with 8hr retention time, demonstrated total removal of helminth eggs (El-Gohary and Nasr, 1999) with another laboratory scale reactor demonstrating 93 =/-5% removal at low up-flow rates of 0.9 m.h-1, though decreasing in a linear fashion with increasing up-flow rate (Yaya-Beas et al, 2015).This efficacy has not been replicated in the real world, an investigation in Brazil indicated a 0.6 log 10 reduction efficacy of the UASB unit with retention time of 5.5hrs in removing helminth eggs (no Taenia spp. present in the raw sewage) and in combination with a baffled polishing pond resulted in complete removal of helminth eggs in 13 of 14 effluent samples with a mean of 0.1 helminth egg/l across all samples (Von Sperling et al, 2002).…”